Listen Before Talk Subframe Configuration in a Wireless Network

ABSTRACT

A first base station receives from a second base station, one or more first parameters identifying a first plurality of subframes as listen-before-talk (LBT) subframes of the second base station. A second plurality of subframes are selected as LBT subframes by the first base station based on the one or more first parameters. The first base station transmits to a wireless device, at least one radio resource control message comprising one or more third parameters identifying the second plurality of subframes as LBT subframes. The first base station performs an LBT procedure in a subframe of the second plurality of subframes. The first base station transmits a burst based on the LBT procedure indicating a clear channel. The burst is configurable to start in the subframe based on the subframe being identified as an LBT subframe.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Ser. No. 15/284,301, filed Oct. 3,2016, which claims the benefit of U.S. Provisional Application No.62/235,813, filed Oct. 1, 2015, which is hereby incorporated byreference in its entirety.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Examples of several of the various embodiments of the present inventionare described herein with reference to the drawings.

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present invention.

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers in a carrier group as per an aspect of anembodiment of the present invention.

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present invention.

FIG. 4 is a block diagram of a base station and a wireless device as peran aspect of an embodiment of the present invention.

FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D are example diagrams for uplinkand downlink signal transmission as per an aspect of an embodiment ofthe present invention.

FIG. 6 is an example diagram for a protocol structure with CA and DC asper an aspect of an embodiment of the present invention.

FIG. 7 is an example diagram for a protocol structure with CA and DC asper an aspect of an embodiment of the present invention.

FIG. 8 shows example TAG configurations as per an aspect of anembodiment of the present invention.

FIG. 9 is an example message flow in a random access process in asecondary TAG as per an aspect of an embodiment of the presentinvention.

FIG. 10 is an example diagram depicting a downlink burst as per anaspect of an embodiment of the present invention.

FIG. 11A and FIG. 11B are example diagrams depicting subframeconfiguration as per an aspect of an embodiment of the presentinvention.

FIG. 12 is an example diagram depicting subframe configuration in aplurality of base stations as per an aspect of an embodiment of thepresent invention.

FIG. 13 is an example flow diagram as per an aspect of an embodiment ofthe present invention.

FIG. 14 is an example flow diagram as per an aspect of an embodiment ofthe present invention.

FIG. 15 is an example flow diagram as per an aspect of an embodiment ofthe present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Example embodiments of the present invention enable operation of carrieraggregation. Embodiments of the technology disclosed herein may beemployed in the technical field of multicarrier communication systems.More particularly, the embodiments of the technology disclosed hereinmay relate to signal timing in multicarrier communication systems.

The following Acronyms are used throughout the present disclosure:

ASIC application-specific integrated circuit

BPSK binary phase shift keying

CA carrier aggregation

CSI channel state information

CDMA code division multiple access

CSS common search space

CPLD complex programmable logic devices

CC component carrier

DL downlink

DCI downlink control information

DC dual connectivity

EPC evolved packet core

E-UTRAN evolved-universal terrestrial radio access network

FPGA field programmable gate arrays

FDD frequency division multiplexing

HDL hardware description languages

HARQ hybrid automatic repeat request

IE information element

LTE long term evolution

MCG master cell group

MeNB master evolved node B

MIB master information block

MAC media access control

MAC media access control

MME mobility management entity

NAS non-access stratum

OFDM orthogonal frequency division multiplexing

PDCP packet data convergence protocol

PDU packet data unit

PHY physical

PDCCH physical downlink control channel

PHICH physical HARQ indicator channel

PUCCH physical uplink control channel

PUSCH physical uplink shared channel

PCell primary cell

PCell primary cell

PCC primary component carrier

PSCell primary secondary cell

pTAG primary timing advance group

QAM quadrature amplitude modulation

QPSK quadrature phase shift keying

RBG Resource Block Groups

RLC radio link control

RRC radio resource control

RA random access

RB resource blocks

SCC secondary component carrier

SCell secondary cell

Scell secondary cells

SCG secondary cell group

SeNB secondary evolved node B

sTAGs secondary timing advance group

SDU service data unit

S-GW serving gateway

SRB signaling radio bearer

SC-OFDM single carrier-OFDM

SFN system frame number

SIB system information block

TAI tracking area identifier

TAT time alignment timer

TDD time division duplexing

TDMA time division multiple access

TA timing advance

TAG timing advance group

TB transport block

UL uplink

UE user equipment

VHDL VHSIC hardware description language

Example embodiments of the invention may be implemented using variousphysical layer modulation and transmission mechanisms. Exampletransmission mechanisms may include, but are not limited to: CDMA, OFDM,TDMA, Wavelet technologies, and/or the like. Hybrid transmissionmechanisms such as TDMA/CDMA, and OFDM/CDMA may also be employed.Various modulation schemes may be applied for signal transmission in thephysical layer. Examples of modulation schemes include, but are notlimited to: phase, amplitude, code, a combination of these, and/or thelike. An example radio transmission method may implement QAM using BPSK,QPSK, 16-QAM, 64-QAM, 256-QAM, and/or the like. Physical radiotransmission may be enhanced by dynamically or semi-dynamically changingthe modulation and coding scheme depending on transmission requirementsand radio conditions.

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present invention. As illustrated in thisexample, arrow(s) in the diagram may depict a subcarrier in amulticarrier OFDM system. The OFDM system may use technology such asOFDM technology, DFTS-OFDM, SC-OFDM technology, or the like. Forexample, arrow 101 shows a subcarrier transmitting information symbols.FIG. 1 is for illustration purposes, and a typical multicarrier OFDMsystem may include more subcarriers in a carrier. For example, thenumber of subcarriers in a carrier may be in the range of 10 to 10,000subcarriers. FIG. 1 shows two guard bands 106 and 107 in a transmissionband. As illustrated in FIG. 1, guard band 106 is between subcarriers103 and subcarriers 104. The example set of subcarriers A 102 includessubcarriers 103 and subcarriers 104. FIG. 1 also illustrates an exampleset of subcarriers B 105. As illustrated, there is no guard band betweenany two subcarriers in the example set of subcarriers B 105. Carriers ina multicarrier OFDM communication system may be contiguous carriers,non-contiguous carriers, or a combination of both contiguous andnon-contiguous carriers.

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers as per an aspect of an embodiment of the presentinvention. A multicarrier OFDM communication system may include one ormore carriers, for example, ranging from 1 to 10 carriers. Carrier A 204and carrier B 205 may have the same or different timing structures.Although FIG. 2 shows two synchronized carriers, carrier A 204 andcarrier B 205 may or may not be synchronized with each other. Differentradio frame structures may be supported for FDD and TDD duplexmechanisms. FIG. 2 shows an example FDD frame timing. Downlink anduplink transmissions may be organized into radio frames 201. In thisexample, radio frame duration is 10 msec. Other frame durations, forexample, in the range of 1 to 100 msec may also be supported. In thisexample, each 10 ms radio frame 201 may be divided into ten equallysized subframes 202. Other subframe durations such as including 0.5msec, 1 msec, 2 msec, and 5 msec may also be supported. Subframe(s) mayconsist of two or more slots (e.g. slots 206 and 207). For the exampleof FDD, 10 subframes may be available for downlink transmission and 10subframes may be available for uplink transmissions in each 10 msinterval. Uplink and downlink transmissions may be separated in thefrequency domain. Slot(s) may include a plurality of OFDM symbols 203.The number of OFDM symbols 203 in a slot 206 may depend on the cyclicprefix length and subcarrier spacing.

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present invention. The resource grid structure intime 304 and frequency 305 is illustrated in FIG. 3. The quantity ofdownlink subcarriers or RBs (in this example 6 to 100 RBs) may depend,at least in part, on the downlink transmission bandwidth 306 configuredin the cell. The smallest radio resource unit may be called a resourceelement (e.g. 301). Resource elements may be grouped into resourceblocks (e.g. 302). Resource blocks may be grouped into larger radioresources called Resource Block Groups (RBG) (e.g. 303). The transmittedsignal in slot 206 may be described by one or several resource grids ofa plurality of subcarriers and a plurality of OFDM symbols. Resourceblocks may be used to describe the mapping of certain physical channelsto resource elements. Other pre-defined groupings of physical resourceelements may be implemented in the system depending on the radiotechnology. For example, 24 subcarriers may be grouped as a radio blockfor a duration of 5 msec. In an illustrative example, a resource blockmay correspond to one slot in the time domain and 180 kHz in thefrequency domain (for 15 KHz subcarrier bandwidth and 12 subcarriers).

FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D are example diagrams for uplinkand downlink signal transmission as per an aspect of an embodiment ofthe present invention. FIG. 5A shows an example uplink physical channel.The baseband signal representing the physical uplink shared channel mayperform the following processes. These functions are illustrated asexamples and it is anticipated that other mechanisms may be implementedin various embodiments. The functions may comprise scrambling,modulation of scrambled bits to generate complex-valued symbols, mappingof the complex-valued modulation symbols onto one or severaltransmission layers, transform precoding to generate complex-valuedsymbols, precoding of the complex-valued symbols, mapping of precodedcomplex-valued symbols to resource elements, generation ofcomplex-valued time-domain DFTS-OFDM/SC-FDMA signal for each antennaport, and/or the like.

Example modulation and up-conversion to the carrier frequency of thecomplex-valued DFTS-OFDM/SC-FDMA baseband signal for each antenna portand/or the complex-valued PRACH baseband signal is shown in FIG. 5B.Filtering may be employed prior to transmission.

An example structure for Downlink Transmissions is shown in FIG. 5C. Thebaseband signal representing a downlink physical channel may perform thefollowing processes. These functions are illustrated as examples and itis anticipated that other mechanisms may be implemented in variousembodiments. The functions include scrambling of coded bits in each ofthe codewords to be transmitted on a physical channel; modulation ofscrambled bits to generate complex-valued modulation symbols; mapping ofthe complex-valued modulation symbols onto one or several transmissionlayers; precoding of the complex-valued modulation symbols on each layerfor transmission on the antenna ports; mapping of complex-valuedmodulation symbols for each antenna port to resource elements;generation of complex-valued time-domain OFDM signal for each antennaport, and/or the like.

Example modulation and up-conversion to the carrier frequency of thecomplex-valued OFDM baseband signal for each antenna port is shown inFIG. 5D. Filtering may be employed prior to transmission.

FIG. 4 is an example block diagram of a base station 401 and a wirelessdevice 406, as per an aspect of an embodiment of the present invention.A communication network 400 may include at least one base station 401and at least one wireless device 406. The base station 401 may includeat least one communication interface 402, at least one processor 403,and at least one set of program code instructions 405 stored innon-transitory memory 404 and executable by the at least one processor403. The wireless device 406 may include at least one communicationinterface 407, at least one processor 408, and at least one set ofprogram code instructions 410 stored in non-transitory memory 409 andexecutable by the at least one processor 408. Communication interface402 in base station 401 may be configured to engage in communicationwith communication interface 407 in wireless device 406 via acommunication path that includes at least one wireless link 411.Wireless link 411 may be a bi-directional link. Communication interface407 in wireless device 406 may also be configured to engage in acommunication with communication interface 402 in base station 401. Basestation 401 and wireless device 406 may be configured to send andreceive data over wireless link 411 using multiple frequency carriers.According to some of the various aspects of embodiments, transceiver(s)may be employed. A transceiver is a device that includes both atransmitter and receiver. Transceivers may be employed in devices suchas wireless devices, base stations, relay nodes, and/or the like.Example embodiments for radio technology implemented in communicationinterface 402, 407 and wireless link 411 are illustrated are FIG. 1,FIG. 2, FIG. 3, FIG. 5, and associated text.

An interface may be a hardware interface, a firmware interface, asoftware interface, and/or a combination thereof. The hardware interfacemay include connectors, wires, electronic devices such as drivers,amplifiers, and/or the like. A software interface may include codestored in a memory device to implement protocol(s), protocol layers,communication drivers, device drivers, combinations thereof, and/or thelike. A firmware interface may include a combination of embeddedhardware and code stored in and/or in communication with a memory deviceto implement connections, electronic device operations, protocol(s),protocol layers, communication drivers, device drivers, hardwareoperations, combinations thereof, and/or the like.

The term configured may relate to the capacity of a device whether thedevice is in an operational or non-operational state. Configured mayalso refer to specific settings in a device that effect the operationalcharacteristics of the device whether the device is in an operational ornon-operational state. In other words, the hardware, software, firmware,registers, memory values, and/or the like may be “configured” within adevice, whether the device is in an operational or nonoperational state,to provide the device with specific characteristics. Terms such as “acontrol message to cause in a device” may mean that a control messagehas parameters that may be used to configure specific characteristics inthe device, whether the device is in an operational or non-operationalstate.

According to some of the various aspects of embodiments, an LTE networkmay include a multitude of base stations, providing a user planePDCP/RLC/MAC/PHY and control plane (RRC) protocol terminations towardsthe wireless device. The base station(s) may be interconnected withother base station(s) (e.g. employing an X2 interface). The basestations may also be connected employing, for example, an S1 interfaceto an EPC. For example, the base stations may be interconnected to theMME employing the S1-MME interface and to the S-G) employing the S1-Uinterface. The S1 interface may support a many-to-many relation betweenMMEs/Serving Gateways and base stations. A base station may include manysectors for example: 1, 2, 3, 4, or 6 sectors. A base station mayinclude many cells, for example, ranging from 1 to 50 cells or more. Acell may be categorized, for example, as a primary cell or secondarycell. At RRC connection establishment/re-establishment/handover, oneserving cell may provide the NAS (non-access stratum) mobilityinformation (e.g. TAI), and at RRC connection re-establishment/handover,one serving cell may provide the security input. This cell may bereferred to as the Primary Cell (PCell). In the downlink, the carriercorresponding to the PCell may be the Downlink Primary Component Carrier(DL PCC), while in the uplink, it may be the Uplink Primary ComponentCarrier (UL PCC). Depending on wireless device capabilities, SecondaryCells (SCells) may be configured to form together with the PCell a setof serving cells. In the downlink, the carrier corresponding to an SCellmay be a Downlink Secondary Component Carrier (DL SCC), while in theuplink, it may be an Uplink Secondary Component Carrier (UL SCC). AnSCell may or may not have an uplink carrier.

A cell, comprising a downlink carrier and optionally an uplink carrier,may be assigned a physical cell ID and a cell index. A carrier (downlinkor uplink) may belong to only one cell. The cell ID or Cell index mayalso identify the downlink carrier or uplink carrier of the cell(depending on the context it is used). In the specification, cell ID maybe equally referred to a carrier ID, and cell index may be referred tocarrier index. In implementation, the physical cell ID or cell index maybe assigned to a cell. A cell ID may be determined using asynchronization signal transmitted on a downlink carrier. A cell indexmay be determined using RRC messages. For example, when thespecification refers to a first physical cell ID for a first downlinkcarrier, the specification may mean the first physical cell ID is for acell comprising the first downlink carrier. The same concept may applyto, for example, carrier activation. When the specification indicatesthat a first carrier is activated, the specification may equally meanthat the cell comprising the first carrier is activated.

Embodiments may be configured to operate as needed. The disclosedmechanism may be performed when certain criteria are met, for example,in a wireless device, a base station, a radio environment, a network, acombination of the above, and/or the like. Example criteria may bebased, at least in part, on for example, traffic load, initial systemset up, packet sizes, traffic characteristics, a combination of theabove, and/or the like. When the one or more criteria are met, variousexample embodiments may be applied. Therefore, it may be possible toimplement example embodiments that selectively implement disclosedprotocols.

A base station may communicate with a mix of wireless devices. Wirelessdevices may support multiple technologies, and/or multiple releases ofthe same technology. Wireless devices may have some specificcapability(ies) depending on its wireless device category and/orcapability(ies). A base station may comprise multiple sectors. When thisdisclosure refers to a base station communicating with a plurality ofwireless devices, this disclosure may refer to a subset of the totalwireless devices in a coverage area. This disclosure may refer to, forexample, a plurality of wireless devices of a given LTE release with agiven capability and in a given sector of the base station. Theplurality of wireless devices in this disclosure may refer to a selectedplurality of wireless devices, and/or a subset of total wireless devicesin a coverage area which perform according to disclosed methods, and/orthe like. There may be a plurality of wireless devices in a coveragearea that may not comply with the disclosed methods, for example,because those wireless devices perform based on older releases of LTEtechnology.

FIG. 6 and FIG. 7 are example diagrams for protocol structure with CAand DC as per an aspect of an embodiment of the present invention.E-UTRAN may support Dual Connectivity (DC) operation whereby a multipleRX/TX UE in RRC_CONNECTED may be configured to utilize radio resourcesprovided by two schedulers located in two eNBs connected via a non-idealbackhaul over the X2 interface. eNBs involved in DC for a certain UE mayassume two different roles: an eNB may either act as an MeNB or as anSeNB. In DC a UE may be connected to one MeNB and one SeNB. Mechanismsimplemented in DC may be extended to cover more than two eNBs. FIG. 7illustrates one example structure for the UE side MAC entities when aMaster Cell Group (MCG) and a Secondary Cell Group (SCG) are configured,and it may not restrict implementation. Media Broadcast MulticastService (MBMS) reception is not shown in this figure for simplicity.

In DC, the radio protocol architecture that a particular bearer uses maydepend on how the bearer is setup. Three alternatives may exist, an MCGbearer, an SCG bearer and a split bearer as shown in FIG. 6. RRC may belocated in MeNB and SRBs may be configured as a MCG bearer type and mayuse the radio resources of the MeNB. DC may also be described as havingat least one bearer configured to use radio resources provided by theSeNB. DC may or may not be configured/implemented in example embodimentsof the invention.

In the case of DC, the UE may be configured with two MAC entities: oneMAC entity for MeNB, and one MAC entity for SeNB. In DC, the configuredset of serving cells for a UE may comprise of two subsets: the MasterCell Group (MCG) containing the serving cells of the MeNB, and theSecondary Cell Group (SCG) containing the serving cells of the SeNB. Fora SCG, one or more of the following may be applied: at least one cell inthe SCG has a configured UL CC and one of them, named PSCell (or PCellof SCG, or sometimes called PCell), is configured with PUCCH resources;when the SCG is configured, there may be at least one SCG bearer or oneSplit bearer; upon detection of a physical layer problem or a randomaccess problem on a PSCell, or the maximum number of RLC retransmissionshas been reached associated with the SCG, or upon detection of an accessproblem on a PSCell during a SCG addition or a SCG change: a RRCconnection re-establishment procedure may not be triggered, ULtransmissions towards cells of the SCG are stopped, a MeNB may beinformed by the UE of a SCG failure type, for split bearer, the DL datatransfer over the MeNB is maintained; the RLC AM bearer may beconfigured for the split bearer; like PCell, PSCell may not bede-activated; PSCell may be changed with a SCG change (e.g. withsecurity key change and a RACH procedure); and/or neither a directbearer type change between a Split bearer and a SCG bearer norsimultaneous configuration of a SCG and a Split bearer are supported.

With respect to the interaction between a MeNB and a SeNB, one or moreof the following principles may be applied: the MeNB may maintain theRRM measurement configuration of the UE and may, (e.g., based onreceived measurement reports or traffic conditions or bearer types),decide to ask a SeNB to provide additional resources (serving cells) fora UE; upon receiving a request from the MeNB, a SeNB may create acontainer that may result in the configuration of additional servingcells for the UE (or decide that it has no resource available to do so);for UE capability coordination, the MeNB may provide (part of) the ASconfiguration and the UE capabilities to the SeNB; the MeNB and the SeNBmay exchange information about a UE configuration by employing of RRCcontainers (inter-node messages) carried in X2 messages; the SeNB mayinitiate a reconfiguration of its existing serving cells (e.g., PUCCHtowards the SeNB); the SeNB may decide which cell is the PSCell withinthe SCG; the MeNB may not change the content of the RRC configurationprovided by the SeNB; in the case of a SCG addition and a SCG SCelladdition, the MeNB may provide the latest measurement results for theSCG cell(s); both a MeNB and a SeNB may know the SFN and subframe offsetof each other by OAM, (e.g., for the purpose of DRX alignment andidentification of a measurement gap). In an example, when adding a newSCG SCell, dedicated RRC signalling may be used for sending requiredsystem information of the cell as for CA, except for the SFN acquiredfrom a MIB of the PSCell of a SCG.

In an example, serving cells may be grouped in a TA group (TAG). Servingcells in one TAG may use the same timing reference. For a given TAG,user equipment (UE) may use at least one downlink carrier as a timingreference. For a given TAG, a UE may synchronize uplink subframe andframe transmission timing of uplink carriers belonging to the same TAG.In an example, serving cells having an uplink to which the same TAapplies may correspond to serving cells hosted by the same receiver. AUE supporting multiple TAs may support two or more TA groups. One TAgroup may contain the PCell and may be called a primary TAG (pTAG). In amultiple TAG configuration, at least one TA group may not contain thePCell and may be called a secondary TAG (sTAG). In an example, carrierswithin the same TA group may use the same TA value and/or the sametiming reference. When DC is configured, cells belonging to a cell group(MCG or SCG) may be grouped into multiple TAGs including a pTAG and oneor more sTAGs.

FIG. 8 shows example TAG configurations as per an aspect of anembodiment of the present invention. In Example 1, pTAG comprises PCell,and an sTAG comprises SCell1. In Example 2, a pTAG comprises a PCell andSCell1, and an sTAG comprises SCell2 and SCell3. In Example 3, pTAGcomprises PCell and SCell1, and an sTAG1 includes SCell2 and SCell3, andsTAG2 comprises SCell4. Up to four TAGs may be supported in a cell group(MCG or SCG) and other example TAG configurations may also be provided.In various examples in this disclosure, example mechanisms are describedfor a pTAG and an sTAG. Some of the example mechanisms may be applied toconfigurations with multiple sTAGs.

In an example, an eNB may initiate an RA procedure via a PDCCH order foran activated SCell. This PDCCH order may be sent on a scheduling cell ofthis SCell. When cross carrier scheduling is configured for a cell, thescheduling cell may be different than the cell that is employed forpreamble transmission, and the PDCCH order may include an SCell index.At least a non-contention based RA procedure may be supported forSCell(s) assigned to sTAG(s).

FIG. 9 is an example message flow in a random access process in asecondary TAG as per an aspect of an embodiment of the presentinvention. An eNB transmits an activation command 600 to activate anSCell. A preamble 602 (Msg1) may be sent by a UE in response to a PDCCHorder 601 on an SCell belonging to an sTAG. In an example embodiment,preamble transmission for SCells may be controlled by the network usingPDCCH format 1A. Msg2 message 603 (RAR: random access response) inresponse to the preamble transmission on the SCell may be addressed toRA-RNTI in a PCell common search space (CSS). Uplink packets 604 may betransmitted on the SCell in which the preamble was transmitted.

According to some of the various aspects of embodiments, initial timingalignment may be achieved through a random access procedure. This mayinvolve a UE transmitting a random access preamble and an eNB respondingwith an initial TA command NTA (amount of timing advance) within arandom access response window. The start of the random access preamblemay be aligned with the start of a corresponding uplink subframe at theUE assuming NTA=0. The eNB may estimate the uplink timing from therandom access preamble transmitted by the UE. The TA command may bederived by the eNB based on the estimation of the difference between thedesired UL timing and the actual UL timing. The UE may determine theinitial uplink transmission timing relative to the correspondingdownlink of the sTAG on which the preamble is transmitted.

The mapping of a serving cell to a TAG may be configured by a servingeNB with RRC signaling. The mechanism for TAG configuration andreconfiguration may be based on RRC signaling. According to some of thevarious aspects of embodiments, when an eNB performs an SCell additionconfiguration, the related TAG configuration may be configured for theSCell. In an example embodiment, an eNB may modify the TAG configurationof an SCell by removing (releasing) the SCell and adding (configuring) anew SCell (with the same physical cell ID and frequency) with an updatedTAG ID. The new SCell with the updated TAG ID may initially be inactivesubsequent to being assigned the updated TAG ID. The eNB may activatethe updated new SCell and start scheduling packets on the activatedSCell. In an example implementation, it may not be possible to changethe TAG associated with an SCell, but rather, the SCell may need to beremoved and a new SCell may need to be added with another TAG. Forexample, if there is a need to move an SCell from an sTAG to a pTAG, atleast one RRC message, for example, at least one RRC reconfigurationmessage, may be send to the UE to reconfigure TAG configurations byreleasing the SCell and then configuring the SCell as a part of the pTAG(when an SCell is added/configured without a TAG index, the SCell may beexplicitly assigned to the pTAG). The PCell may not change its TA groupand may be a member of the pTAG.

The purpose of an RRC connection reconfiguration procedure may be tomodify an RRC connection, (e.g. to establish, modify and/or release RBs,to perform handover, to setup, modify, and/or release measurements, toadd, modify, and/or release SCells). If the received RRC ConnectionReconfiguration message includes the sCellToReleaseList, the UE mayperform an SCell release. If the received RRC Connection Reconfigurationmessage includes the sCellToAddModList, the UE may perform SCelladditions or modification.

In LTE Release-10 and Release-11 CA, a PUCCH is only transmitted on thePCell (PSCell) to an eNB. In LTE-Release 12 and earlier, a UE maytransmit PUCCH information on one cell (PCell or PSCell) to a given eNB.

As the number of CA capable UEs and also the number of aggregatedcarriers increase, the number of PUCCHs and also the PUCCH payload sizemay increase. Accommodating the PUCCH transmissions on the PCell maylead to a high PUCCH load on the PCell. A PUCCH on an SCell may beintroduced to offload the PUCCH resource from the PCell. More than onePUCCH may be configured for example, a PUCCH on a PCell and anotherPUCCH on an SCell. In the example embodiments, one, two or more cellsmay be configured with PUCCH resources for transmitting CSI/ACK/NACK toa base station. Cells may be grouped into multiple PUCCH groups, and oneor more cell within a group may be configured with a PUCCH. In anexample configuration, one SCell may belong to one PUCCH group. SCellswith a configured PUCCH transmitted to a base station may be called aPUCCH SCell, and a cell group with a common PUCCH resource transmittedto the same base station may be called a PUCCH group.

In an example embodiment, a MAC entity may have a configurable timertimeAlignmentTimer per TAG. The timeAlignmentTimer may be used tocontrol how long the MAC entity considers the Serving Cells belonging tothe associated TAG to be uplink time aligned. The MAC entity may, when aTiming Advance Command MAC control element is received, apply the TimingAdvance Command for the indicated TAG; start or restart thetimeAlignmentTimer associated with the indicated TAG. The MAC entitymay, when a Timing Advance Command is received in a Random AccessResponse message for a serving cell belonging to a TAG and/or if theRandom Access Preamble was not selected by the MAC entity, apply theTiming Advance Command for this TAG and start or restart thetimeAlignmentTimer associated with this TAG. Otherwise, if thetimeAlignmentTimer associated with this TAG is not running, the TimingAdvance Command for this TAG may be applied and the timeAlignmentTimerassociated with this TAG started. When the contention resolution isconsidered not successful, a timeAlignmentTimer associated with this TAGmay be stopped. Otherwise, the MAC entity may ignore the received TimingAdvance Command.

In example embodiments, a timer is running once it is started, until itis stopped or until it expires; otherwise it may not be running. A timercan be started if it is not running or restarted if it is running. Forexample, a timer may be started or restarted from its initial value.

Example embodiments of the invention may enable operation ofmulti-carrier communications. Other example embodiments may comprise anon-transitory tangible computer readable media comprising instructionsexecutable by one or more processors to cause operation of multi-carriercommunications. Yet other example embodiments may comprise an article ofmanufacture that comprises a non-transitory tangible computer readablemachine-accessible medium having instructions encoded thereon forenabling programmable hardware to cause a device (e.g. wirelesscommunicator, UE, base station, etc.) to enable operation ofmulti-carrier communications. The device may include processors, memory,interfaces, and/or the like. Other example embodiments may comprisecommunication networks comprising devices such as base stations,wireless devices (or user equipment: UE), servers, switches, antennas,and/or the like.

The amount of data traffic carried over cellular networks is expected toincrease for many years to come. The number of users/devices isincreasing and each user/device accesses an increasing number andvariety of services, e.g. video delivery, large files, images. Thisrequires not only high capacity in the network, but also provisioningvery high data rates to meet customers' expectations on interactivityand responsiveness. More spectrum is therefore needed for cellularoperators to meet the increasing demand. Considering user expectationsof high data rates along with seamless mobility, it is beneficial thatmore spectrum be made available for deploying macro cells as well assmall cells for cellular systems.

Striving to meet the market demands, there has been increasing interestfrom operators in deploying some complementary access utilizingunlicensed spectrum to meet the traffic growth. This is exemplified bythe large number of operator-deployed Wi-Fi networks and the 3GPPstandardization of LTE/WLAN interworking solutions. This interestindicates that unlicensed spectrum, when present, can be an effectivecomplement to licensed spectrum for cellular operators to helpaddressing the traffic explosion in some scenarios, such as hotspotareas. LAA offers an alternative for operators to make use of unlicensedspectrum while managing one radio network, thus offering newpossibilities for optimizing the network's efficiency.

In an example embodiment, Listen-before-talk (clear channel assessment)may be implemented for transmission in an LAA cell. In alisten-before-talk (LBT) procedure, equipment may apply a clear channelassessment (CCA) check before using the channel. For example, the CCAutilizes at least energy detection to determine the presence or absenceof other signals on a channel in order to determine if a channel isoccupied or clear, respectively. For example, European and Japaneseregulations mandate the usage of LBT in the unlicensed bands. Apart fromregulatory requirements, carrier sensing via LBT may be one way for fairsharing of the unlicensed spectrum.

In an example embodiment, discontinuous transmission on an unlicensedcarrier with limited maximum transmission duration may be enabled. Someof these functions may be supported by one or more signals to betransmitted from the beginning of a discontinuous LAA downlinktransmission. Channel reservation may be enabled by the transmission ofsignals, by an LAA node, after gaining channel access via a successfulLBT operation, so that other nodes that receive the transmitted signalwith energy above a certain threshold sense the channel to be occupied.Functions that may need to be supported by one or more signals for LAAoperation with discontinuous downlink transmission may include one ormore of the following: detection of the LAA downlink transmission(including cell identification) by UEs; time & frequency synchronizationof UEs.

In an example embodiment, DL LAA design may employ subframe boundaryalignment according to LTE-A carrier aggregation timing relationshipsacross serving cells aggregated by CA. This may not imply that the eNBtransmissions can start only at the subframe boundary. LAA may supporttransmitting PDSCH when not all OFDM symbols are available fortransmission in a subframe according to LBT. Delivery of necessarycontrol information for the PDSCH may also be supported.

LBT procedure may be employed for fair and friendly coexistence of LAAwith other operators and technologies operating in unlicensed spectrum.LBT procedures on a node attempting to transmit on a carrier inunlicensed spectrum require the node to perform a clear channelassessment to determine if the channel is free for use. An LBT proceduremay involve at least energy detection to determine if the channel isbeing used. For example, regulatory requirements in some regions, e.g.,in Europe, specify an energy detection threshold such that if a nodereceives energy greater than this threshold, the node assumes that thechannel is not free. While nodes may follow such regulatoryrequirements, a node may optionally use a lower threshold for energydetection than that specified by regulatory requirements. In an example,LAA may employ a mechanism to adaptively change the energy detectionthreshold, e.g., LAA may employ a mechanism to adaptively lower theenergy detection threshold from an upper bound. Adaptation mechanism maynot preclude static or semi-static setting of the threshold. In anexample Category 4 LBT mechanism or other type of LBT mechanisms may beimplemented.

Various example LBT mechanisms may be implemented. In an example, forsome signals, in some implementation scenarios, in some situations,and/or in some frequencies no LBT procedure may performed by thetransmitting entity. In an example, Category 2 (e.g. LBT without randomback-off) may be implemented. The duration of time that the channel issensed to be idle before the transmitting entity transmits may bedeterministic. In an example, Category 3 (e.g. LBT with random back-offwith a contention window of fixed size) may be implemented. The LBTprocedure may have the following procedure as one of its components. Thetransmitting entity may draw a random number N within a contentionwindow. The size of the contention window may be specified by theminimum and maximum value of N. The size of the contention window may befixed or configurable. The random number N may be employed in the LBTprocedure to determine the duration of time that the channel is sensedto be idle before the transmitting entity transmits on the channel. Inan example, Category 4 (e.g. LBT with random back-off with a contentionwindow of variable size) may be implemented. The transmitting entity maydraw a random number N within a contention window. The size ofcontention window may be specified by the minimum and maximum value ofN. The transmitting entity may vary the size of the contention windowwhen drawing the random number N. The random number N is used in the LBTprocedure to determine the duration of time that the channel is sensedto be idle before the transmitting entity transmits on the channel. Inan example, an eNB may transmit one or more LBT configuration parametersin one or more RRC messages and/or one or more PDCCH DCIs. In anexample, some of the LBT parameters may be configured via RRC message(s)and some other LBT parameters may be signaled to a UE via PDCCH DCI(e.g. a DCI including the UL grant).

LAA may employ uplink LBT at the UE. The UL LBT scheme may be differentfrom the DL LBT scheme (e.g. by using different LBT mechanisms orparameters) for example, since the LAA UL is based on scheduled accesswhich affects a UE's channel contention opportunities. Otherconsiderations motivating a different UL LBT scheme include, but are notlimited to, multiplexing of multiple UEs in a single subframe.

In an example, a DL transmission burst may be a continuous transmissionfrom a DL transmitting node with no transmission immediately before orafter from the same node on the same CC. An UL transmission burst from aUE perspective may be a continuous transmission from a UE with notransmission immediately before or after from the same UE on the sameCC. In an example, UL transmission burst is defined from a UEperspective. In an example, an UL transmission burst may be defined froman eNB perspective. In an example, in case of an eNB operating DL+UL LAAover the same unlicensed carrier, DL transmission burst(s) and ULtransmission burst(s) on LAA may be scheduled in a TDM manner over thesame unlicensed carrier. For example, an instant in time may be part ofa DL transmission burst or an UL transmission burst.

The following signals or combination of the following signals mayprovide functionality for the UE's time/frequency synchronization forthe reception of a DL transmission burst in LAA SCell(s): a) servingcell's DRS for RRM measurement (DRS for RRM measurement may be used atleast for coarse time/frequency synchronization), b) reference signalsembedded within DL transmission bursts (e.g. CRS and/or DMRS), and/or c)primary/secondary synchronization signals. If there is an additionalreference signal, this signal may be used. Reference signals may be usedat least for fine time/frequency synchronization. Other candidates(e.g., initial signal, DRS) may be employed for synchronization.

DRS for RRM may also support functionality for demodulation of potentialbroadcast data multiplexed with DRS transmission. Other mechanism orsignals (e.g., initial signal, DRS) for time/frequency synchronizationmay be needed to support reception of DL transmission burst.

In an example embodiment, DRS may be used at least for coarsetime/frequency synchronization. Reference signals (e.g., CRS and/orDMRS) within DL transmission bursts may be used at least for finetime/frequency synchronization. Once the UE detects DRS and achievescoarse time/frequency synchronization based on that, UE may keeptracking on the synchronization using reference signals embedded inother DL TX bursts and may also use DRS. In an example, a UE may utilizeDRS and/or reference signals embedded within DL transmission bursttargeting the UE. In another example, a UE may utilize DRS and/orreference signals embedded within many available DL transmission burstsfrom the serving cell (to the UE and other UEs).

The discovery signal used for cell discovery/RRM measurement (e.g.opportunistic transmission within configured DMTC) may be used formaintaining at least coarse synchronization with the LAA cell (e.g. <±3μs timing synchronization error and <±0.1 ppm frequency synchronizationerror). DRS may be subject to LBT. Inter-DRS latency generally getsworse as Wi-Fi traffic load increases. It is noted that the inter-DRSlatency can be rather significant. In example scenario, there may be 55%probability that the inter-DRS latency is 40 ms and there is 5%probability that inter-DRS latency is ≥440 ms. The inter-DRS latency asseen by the UE may be worse considering the possibility of misdetectionby the UE. Discovery signal misdetection may be due to actualmisdetection or due to UE unavailable for detection because of DRXinter-frequency measurement during DMTC occasion.

Depending on LAA DRS design, OFDM symbol boundary may be obtained byDRS. PCell and SCell timing difference may be kept, ±30 usec order. Theaggregated cells may be synchronized to some extent, e.g. aligned frametiming and SFN. Thus, similar requirement may be applied to the PCelland LAA cells on the unlicensed band. In an example, a UE may notutilize timing and frequency of the PCell for coarse synchronization ofLAA cells since the timing offset may be up to ˜30 us (e.g. non-located)and frequency reference may not be reliable due to the band distancebetween PCell and LAA cell (2 GHz Pcell and 5 GHz LAA cell). PCelltiming information also may be used for time synchronization at subframeor frame level. SCell(s) may employ the same frame number and subframenumber as the PCell.

PCell timing information may provide some information for symbolsynchronization. By synchronizing PCell, frequency difference observedby UE between PCell and LAA Scell may be up to 0.6 ppm. For example,after 300 ms, the amount of the time drift may be 0.18 usec at most. ForLAA, path delay may be relatively small as the target coverage is small.With timing drift, the multi-path delay may be within cyclic prefixlength.

According to some of the various aspects of embodiments, a UE mayutilize a licensed band carrier as a reference for time/frequencysynchronization for CA of licensed carrier and unlicensed carrier, forexample when they are in the same group (e.g. co-located). Whennon-collocated eNBs support licensed band PCell and unlicensed bandSCell separately in a CA scenario, there may exist maximum ˜30 us timingdifference between PCell and unlicensed band SCell. In an exampleembodiment, the frequency difference between the UE synchronized withPCell and unlicensed band SCell may observe at most 0.6 ppm. An LAA mayprovide functionality for time/frequency synchronization on unlicensedband at least for non-collocated CA scenario.

Example reasons of frequency difference may be 1) oscillator differenceamong PCell, SCell and UE, 2) Doppler shift and 3) fast fading aspect.The oscillator difference of 0.6 ppm offset in 5 GHz corresponds to 3kHz offset. Subcarrier spacing of LTE numerology is 15 kHz. This offsetmay need to be taken into account before FFT operation. One of thereasons of oscillator frequency variation is the temperature. If thefrequency difference is not obtained at the point of DRS reception, UEmay need to buffer subsequent data transmission until UE obtains thisfrequency difference before FFT. The frequency offset caused by this maybe obtained at the reception of DRS. Doppler shift may be small valuefor a low mobility UE. Fast fading and residual mismatch caused by 1)and 2) may be compensated during demodulation process similar to alicensed band. This may not require introducing additional referencesignals for unlicensed band.

According to some of the various aspects of embodiments, a UE may beconfigured to perform inter-frequency measurements on the carrierfrequency layer using measurement gaps for SCells that are notconfigured yet. SCell receiver may not be turned on and measurements maybe performed using the Pcell receiver. When a cell is added as Scell butnot activated (“deactivated state”), the UE may receive relevant systeminformation for the SCell from the Pcell. UE may be configured toperform measurements on the Scell without measurement gaps. SCellreceiver may need to be occasionally turned on (e.g. for 5 ms every 160ms) for RRM measurements using either CRS or Discovery signals. Cellsmay be added as Scell and activated (“activated state”), then the UE maybe ready to receive PDSCH on the Scell in all subframes. The SCellreceiver may perform (E)PDCCH monitoring in every subframe (forself-scheduling case(s)). SCell receiver may buffer every subframe forpotential PDSCH processing (for both self and cross-carrier schedulingcases).

The eNodeB may configure the UE to measure and report RRM measurements(e.g. including RSSI) on a set of carrier frequencies. Once a suitablecarrier or a set of suitable carriers is determined, carrier selectedmay be added as an SCell by RRC (e.g. with ˜15 ms configuration delay),followed by SCell activation (with ˜24 ms delay). If an SCell isdeactivated, the UE may assume that no signal is transmitted by the LAAcell, except discovery signal may be transmitted when configured. If anSCell is activated, the UE is required to monitor PDCCH/EPDCCH andperform CSI measurement/reporting for the activated SCell. In a U-cell,a UE may not assume that every subframe of activated LAA SCell containstransmission. For LAA carriers, channel access may depend on the LBTprocedure outcome. The network may configure and activate many carriersfor the UE. The scheduler may then dynamically select carrier(s) for DLassignment or UL grant transmission.

According to some of the various aspects of embodiments, the first stageof cell level carrier selection may be during initial set up of a cellby an eNB. The eNB may scan and sense channels for interference or radardetection. eNB may configure the SCells accordingly based on the outcomeof its carrier selection algorithm for efficient load balancing andinterference management. The carrier selection process may be on adifferent time scale from the LBT/CCA procedure prior to transmissionson the carriers in unlicensed spectrum. The RSSI measurement report fromUE may be used to assist the selection at eNB.

According to some of the various aspects of embodiments, the secondstage of cell level carrier selection is after initial set up. Themotivation is that eNB may need to do carrier (re)selection due tostatic load and interference change on some carriers, e.g., a new Wi-FiAP is set up and continuously accesses the carrier causing relativelystatic interference. Therefore, semi-static carrier selection may bebased on the eNB sensing of the averaged interference level, potentialpresence of radar signals if required, and traffic load on the carriersover a relatively longer time scale, as well as RRM measurement from UEsin the cell. Due to the characteristics in unlicensed spectrum, RRMmeasurements on LAA SCells may be enhanced to support better carrierselection. For example, the RSSI measurement may be enhanced usingoccupancy metric indicating the percentage of the time when RSSI isabove a certain threshold. It may be noted that cell level carrierselection may be a long-term (re)selection since the process may berather costly due to the signalling overhead and communicationinterruptions for UEs in a cell and it may also affect the neighbouringcells. Once a suitable set of carriers is identified, they may beconfigured and activated as SCells for UEs. This process may becontinuous in order to keep reassessing the interference environment.Cell-level carrier selection in unlicensed spectrum may be a relativelylong-term (re)selection based on eNB sensing and RRM measurement reportfrom UE. RRM measurement on LAA SCells may be enhanced to support bettercarrier selection.

Carrier selection from UE perspective may be to support carrierselection for a UE among the set of carriers that the eNB has selectedat the cell level. Carrier selection for the UE in unlicensed spectrummay be achieved by configuring a set of the carriers on which the UEsupports simultaneous reception and transmission. The UE may perform RRMmeasurements on the configured carriers and report them to the eNB. TheeNB may then choose which of the carriers to activate and use fortransmission when it has pending data for the UE. The number of carriersto activate may then also be chosen based on the data rate needed andthe RRM measurements for the different carriers. The activation delayfor a carrier before scheduling data on it may be up to ˜24 ms, assumingthat the UE has performed RRM measurement on this carrier prior toreceiving the activation command within DRX cycle. By operating thecarrier selection based on activation and deactivation, the selectionmay also be done in the order of tens of ms.

According to some of the various aspects of embodiments, CRS may not betransmitted in an activated subframe when a burst is not scheduled inthat subframe. If there are no transmissions from the eNB for anextended duration (Toff), UE demodulation performance may be impacteddue to lack of reference symbols for fine time/frequency tracking. Theextent of performance impact depends on the amount of time for whichthere are no eNB transmissions. The impact may be mitigated by morefrequent transmission of discovery signals.

Discovery signals may be transmitted by the eNB even when UEs are notbeing scheduled. Setting discovery signal periodicity based on UE RRMmeasurement requirements (e.g. 160 ms) may be more efficient thansetting the periodicity based on UE fine time/frequency trackingrequirement.

In an example embodiment, Scell deactivation timer for the unlicensedScell may be set to a value closer to (Toff) based on UE finetime/frequency tracking requirements. This may result in more frequenttransmission of activation commands. Activation commands may be neededwhen the eNB has data to schedule to a UE. From the UE perspective,after receiving an activation command in a particular subframe, the UEmay receive CRS in a number (e.g. one or two) of following subframes.The UEs may receive CRS transmissions for a few symbols or subframes,which they may use for settling AGC loop and time-frequency trackingfilters before PDSCH reception on the SCell. UEs may receive CRStransmission (e.g. in a few OFDM symbols) between reception ofactivation command and reception PDSCH on the Scell.

Activating a large number of carriers on dynamic bases may increase theUE power consumption, false alarm probability, and processing powerrequirements. Improved mechanisms are needed to improve efficiency inthe UE and enable fast and dynamic carrier selection/activation in a UE.Novel mechanisms may reduce UE power consumption, reduce false alarmprobability and reduce processing power requirements. Carrier selectionand activation may be enhanced to achieve fast dynamic carrier selection(or switching). A fast activation procedure for the carrier (e.g.shorter than the currently defined 24 ms) may be defined to improveefficiency.

Current SCell activation latency may include the MAC CE decoding latency(˜3-6 ms) and SCell activation preparation time (RF preparation, up to˜18 ms). Implementation of faster processes and hardware may reducethese delays. SCell MAC activation/deactivation signalling isUE-specific. Signalling overhead may be a concern especially if the cellused for transmitting the signal is a macro cell. In an exampleembodiment, a L1 procedure/indicator may be introduced and/or SCellactivation signalling may be enhanced.

Layer one signalling (e.g. PDCCH/EPDCCH from the PCell or anotherserving cell) may be implemented to signal the set of carriers that theUE may monitor for PDCCH/EPDCCH and/or measuring/reporting CSI. Controlsignalling latency may be ˜2 ms (e.g. one 1 ms EPDCCH transmission plus0.5 ms decoding). The DCI format may be of small size for transmissionreliability and overhead reduction. To reduce control signallingoverhead, the signalling may be a UE-common signalling. The indicationmay be sent on a carrier that the UE is currently monitoring.

In an example embodiment, a mechanism based on a L1 indication forstarting/stopping monitoring of up to k activated carriers may beprovided. The UE may be configured with n>=k CCs. k CCs may be activatedvia MAC signalling of SCell activation/deactivation. Then based on LBTprogress over the CCs, a L1 indication is sent to inform which of the kCCs may be monitored by the UE and which may not. The UE may thenreceive data burst(s) on the monitored CCs. Another L1 indication may besent after the bursts to alter which CCs may be monitored since then,and so on. The L1 indication may be explicit (e.g., based on asignalling) or implicit (e.g., based on self-scheduling and UE detectionof scheduling information on the SCell). For this example, fast carrierswitching is done among at most k CCs.

In an example embodiment, a mechanism based on a L1 signalling forstarting/stopping monitoring of up to m activated carriers (the numberof p configured carriers may be m or higher). The activated carriers maybe more than n (e.g., there may be more CCs activated for the UE thanits PDSCH aggregation capability-n). The UE is configured with p CCs,and there may be up to m CCs that are activated via MAC signalling ofSCell activation/deactivation. The UE may not monitor all the activatedCCs. The UE may monitor at most n CCs according a L1 indication. The L1indication needs to be explicit rather than implicit, since an implicitindication may require a UE to monitor all the up to m activatedcarriers at the same time, exceeding the UE's capability. For thisexample, fast carrier switching is done among possibly more than n CCs.

According to some of the various aspects of embodiments, SCellactivation/deactivation enhancements may be considered for fast carrierswitching. SCell activation/deactivation signalling is a MAC signalling.MAC signalling decoding/detection (with or without enhancements) may beslower than L1 signalling decoding/detection. It may involvedecoding/detection of a L1 signalling and furthermore, a PDSCH. If SCellactivation/deactivation is carried by a L1 signalling, it may still beconsidered for fast carrier switching. In an example embodiment, amechanism based on a L1 signalling for activation/deactivation of the pconfigured carriers. The UE is configured with p CCs, but each timethere are at most n CCs are activated via a L1 signalling of SCellactivation/deactivation. For instance, based on LBT progress over theCCs, a L1 signalling is sent to inform which of the p CCs are activated.The UE may receive data burst(s) on the activated CCs. Another L1signalling may be sent after the bursts to alter the activated CCs. Forthis example, fast carrier switching is done among possibly more than nCCs.

The control signalling may be transmitted before the eNB has gainedaccess to the carrier via LBT process. An eNB may inform the UE to start(or stop) monitoring a carrier (whether the UE would receive a burst ornot depends on the presence of PDCCH scheduling information for thecarrier). An indication for starting monitoring may be used for morethan one burst, until an indication for stopping monitoring is sent. Theindication may be sent when the eNB expects the (E) CCA is to completesoon. A purpose of the indication may be to inform a UE to start or stopmonitoring a carrier.

Transmitting the control signalling after the eNB has gained access tothe carrier may incur overhead of the reservation signal (proportionalto the control signalling latency). In an example, the maximumtransmission burst may be 4 ms. An eNB may inform the UE to receive aburst on a carrier. The eNB may send one indication for a burst. Theremay be many short bursts (e.g., one burst may last up to 4 millisecondsin certain regions). The indication may be sent after (E)CCA iscompleted, consuming some portion of the maximum allowed transmissionduration for a burst.

It may still be up to the network to transmit the control signallingbefore or after the channel is occupied. A UE may detect that the burstis from the serving cell (e.g. by confirming PCID). The function of thecontrol signalling is to indicate that the UE may perform DLtransmission burst detection of the serving cell. If a DL burst of theserving cell is detected, UE may monitor for possible PDCCH/EPDCCHand/or measuring the CSI on the indicated SCell.

In an example embodiment, a UE may be configured with a number ofcarriers potentially exceeding the maximum number of carriers over whichthe UE may aggregate PDSCH. RRM measurements over the configuredcarriers may be supported, e.g. RSSI-like measurement, extension ofquasi co-location concept to across collocated intra-band carriers,and/or carrier grouping. L1 indication to the UE to start monitoring acarrier, which is selected from the configured carriers by the eNB maybe supported.

According to some of the various aspects of embodiments, an eNB mayconfigure UE with more component carriers which may potentially exceedthe maximum number of carriers over which the UE may aggregate PDSCH.Then eNB may activate one or more carriers among the configured carriersto UE by the existing signalling, e.g. MAC signalling. UE may bescheduled on the one or more activated carriers dynamically based on theLBT mechanism.

A UE may switch to receive on any carrier within a set of carriersselected by the serving eNB as fast as subframe/symbol-level, while thenumber of carriers within the set may potentially exceed the maximumnumber of carriers over which the UE may aggregate PDSCH. Whichcarrier(s) the UE may switch to is per eNB indication. When the UE isindicated with the carrier(s) it may switch to, the UE may start tomonitor the indicated carrier(s), e.g. within a few subframes, and maystop monitoring other carriers. By monitoring a carrier it meant tobuffer and attempt to detect the control channels and other associatedchannels. The eNB indication may instruct the UE to switch to theindicated carrier(s) and monitor the carrier(s). The eNB may notinstruct the UE to switch to monitor on more carriers than its PDSCHaggregation capability in a given subframe. The eNB may not schedule theUE on more carriers than its PDSCH aggregation capability. SCellconfiguration enhancements may allow both semi-static and fast carrierswitching with reduced transition time. The delay associated with theSCell configuration signalling as well as the delay associated with themeasurement process may be decreased.

In an example embodiment, fast carrier switching may support UE toswitch to any carrier within a set of carriers selected by the servingeNB as fast as a few subframes/symbols. The eNB may send an indicationinstructing the UE to switch to the indicated carriers and monitor thecarriers. Then the UE may perform the switching and start monitoring theindicated carriers. The UE stops monitoring other carriers. The eNBindication may be done in L1. A L1 procedure/indicator, or anenhancement of the SCell activation signalling may be introduced.

According to some of the various aspects of embodiments, DRS design mayallow DRS transmission on an LAA SCell to be subject to LBT. Thetransmission of DRS within a DMTC window if LBT is applied to DRS mayconsider many factors. Subjected to LBT, DRS may transmitted in fixedtime position within the configured DMTC. Subject to LBT, DRS may betransmitted in at least one of different time positions within theconfigured DMTC. The number of different time positions may berestricted. One possibility is one-time position in the subframe. DRStransmissions outside of the configured DMTC may be supported.

According to some of the various aspects of embodiments, a sensinginterval may allow the start of a DL transmission burst (which may notstart with the DRS) containing DRS without PDSCH within the DMTC. Totalsensing period may be greater than one sensing interval. Whether theabove may be used for the case where transmission burst may not containPDSCH but contains DRS, and any other reference signals or channels. TheECCA counter used for LBT category 4 for the PDSCH may be frozen duringDL transmission burst containing DRS without PDSCH

The RS bandwidth and density/pattern of the DRS design for LAA maysupport for RRM measurement based on a single DRS occasion.

According to some of the various aspects of embodiments, Discoverysignal may be transmitted via a successful LBT operation. When the eNBdoes not have access to the channel, the discovery signal burst may notbe transmitted. In an example, the discovery signal periodicity isconfigured to be 40 ms, and it may be possible to receive the discoverysignal at least once in every 160 to 200 ms with a high probability. Forexample, the probability of receiving a discovery signal burst at leastonce in every 160 ms may greater than 97%. The UE may adjust itsreceiver processing to account for the potential absence of discoverysignals due to lack of access to the channel. For instance, the UE maydetect the presence or absence of a particular discovery signal burstusing the PSS, SSS and CRS signals.

According to some of the various aspects of embodiments, the use ofdiscovery signals that may be subject to LBT. A discovery signal burstmay not be transmitted when LBT fails. Data may be transmitted in theintervening subframes. The reference signals along with controlinformation may be used to reserve the channel prior to a discoverysignal or data transmission.

For reception of data on the serving cell, AGC and fine time andfrequency estimation may employ the discovery signals from the servingcell. In an example, time and frequency estimation may be performedusing the PSS, SSS and/or CRS inside the discovery signal subframes. Theuse of two or more CRS ports may enhance synchronization performance.These signals may provide synchronization estimates that are adequatefor the purpose of RRM measurements on the serving and neighboringcells. When data is to be received by the UE in a subframe that occurs asignificant number of subframes after the last reception of a discoverysignal on the serving cell. Fine tuning of the time and frequencyestimates may be performed using the DM-RS and, if present, the CRSwithin the subframe in which data is received, and/or the initialsignal. The signal used to reserve the channel before the actual startof data transmissions (e.g. reservation signal, initial signal, and/orburst indicator) may be used to fine tune time and frequency estimatesbefore the reception of data. When transmitting data after a longabsence of any discovery signal or other transmissions, the eNB maytransmit a signal of longer duration to reserve the channel in order tofacilitate the use of such a signal for timing and frequencyadjustments.

In LTE-A release 12 or before almost blank subframes (ABS) can beconfigured for PCell and PSCell. For example, the UE may not receivedata in an almost blank subframes. ABS may be employed to controlinterference between the base stations. Enhanced ICIC may be implementedin which potentially interfering base station may transmit in differentsubset of subframes. This may reduce inter-cell interference in thenetwork. Implementation of ABS for LAA cells can be inefficient. It mayresult in transmitting short bursts. Implementation of ABS for LAA cellsmay not be efficient for battery power consumption and processing in aneNB, because eNB may perform LBT in a subframe, get access to it, andthen stop transmission when it reaches an ABS subframe even if itsdownlink burst just started. Implementation of ABS may also not beefficient for a UE in terms of blind decoding and battery powerconsumption. New mechanisms may be implemented to enhance interferencemanagement, reduce processing requirements, and increase efficiency whenmultiple cells share an unlicensed frequency band.

In an example embodiment, an eNB transmits one or more RRC message toconfigure a plurality of cells including configuration parameters forone or more LAA cells. The configuration parameters for an LAA cell mayinclude physical and MAC layer parameters for the cell. In an exampleembodiment, the configuration parameters may include one or moreparameters indicating a subset of subframes. The one or more parametersmay include a bitmap indicating the subset of the subframes. Forexample, a 40 bits or 10 bits bitmap may indicate the subset ofsubframes. For example, bit map [0010101001 0010101001 00101010010010101001] may indicate a subset of subframe. Each bit may represent asubframe. The subframes mapped to zero may not be in the subset. Thebitmap may be applicable to subframes starting from a frame and asubframe according to a predefined rule. In an example, a 10-bit bitmap[0010101001] may indicate a subset of subframes consisting of subframes2, 4, 6, and 9 in a plurality of frames.

In an example, the one or more parameters may be used to specify asubframe pattern. The first/leftmost bit corresponds to the subframe #0of the radio frame satisfying SFN mod x=0, where SFN is that of PCelland x is the size of the bit string divided by 10. “1” denotes that thecorresponding subframe is used.

The bitmap format for the one or more parameters is an exampleimplementation. Other formats may be implemented. For example, the oneor more parameters may include a subframe configuration indexidentifying a certain predefined subframe configuration. In an example,the one or more parameters may be presented by a bitmap of for example 6bits which selects a subset of 6 predefined subframes in a frame, andthe other 4 subframes may be configured using another method. Otherexample format for the one or more parameters may be implemented.

In an example no subframe pattern may be configured (the configurationparameter may be released). In such a case all the subframes, or apredefined subset of subframes may be considered as the configuredsubframe for LBT.

In an example embodiment, in an unlicensed cell, a downlink burst may bestarted in the subset of subframes configured by RRC. A burst may notstart in any arbitrary subframes. Possible starting subframe of thedownlink burst may be defined by the subset of subframes identified bythe one or more parameters. When an eNB accesses the channel it maytransmit for a duration of one or more subframes. The duration maydepend on a maximum configured burst duration in an eNB, the dataavailable for transmission, and/or eNB scheduling algorithm. FIG. 10shows an example downlink burst in an unlicensed (e.g. licensed assistedaccess) cell.

The maximum configured burst duration in the example embodiment may beconfigured in the eNB. An eNB may transmit the maximum configured burstduration to a UE employing an RRC configuration message.

An example is shown in the following figure. The eNB may perform LBT fordownlink burst transmission in subframes indicated as 1, and may notperform LBT in subframes indicated as zero. When the eNB obtainedchannel access, then the eNB may transmit for a limited duration oftime.

In an example embodiment, the downlink burst may be applicable todownlink data bursts. Downlink data bursts may be started in the subsetof subframes configured by RRC message. The duration of the DL databurst may depend on eNB configuration, and eNB scheduling mechanism. Inan example embodiment, the maximum duration of a downlink data burst maybe 4 msec.

As shown in example FIG. 11(A), the eNB may transmit a downlink burstduring the subframes indicated as zero in the bitmap. The eNB may notstart a downlink burst in a subframe indicated as zero in the bitmap. Onnon-LBT subframes, base station may not start a burst while it maytransmit an already started burst.

In an example embodiment, the UE may blind decode and monitor for thestart of a downlink burst in the configured subset of subframes. Thismay reduce the processing requirements and battery power consumption ina UE. Various downlink signal/channel blind decoding and monitoringexamples are presented in the example embodiments.

In an example embodiment, the downlink burst may be applicable todownlink bursts, such as DRS, CSI RS, CRS. SS signal and/or otherpredefined signals (e.g. initial signal, burst indicator, etc.).Downlink bursts may be started in the subset of subframes configured byan RRC message. The duration of the DL burst may depend on eNBconfiguration parameters and/or eNB scheduling mechanism. Example FIG.11(B) shows an example embodiment with a short burst duration.

In an example implementation, a similar mechanism may be implemented foruplink subframes assigned to a UE. An LAA cell may be configured with anuplink carrier. When a cell in a UE is configured with uplink, a subsetof subframes may be configured for starting uplink bursts by a UE.Example embodiments may be extended to configure transmission of uplinksignals by UEs.

FIG. 12 shows an example subframe configuration in an exampleembodiment. In the example, BS1, BS2, and BS3 are neighbouring BSs. Inthis example, these BSs do not compete for starting a burst in a givensubframe and a given subframe is assigned to one of the BS1, BS2 andBS3. In this example, BS1 and BS2 share a coverage area. The firstplurality of LBT subframes of BS1 and the second plurality of LBTsubframes of BS2 are disjoint. Such configuration is applicable to BS1,BS2 and BS3. In this example, BS4 may not share a substantial coveragearea with BS3. BS3 and BS4 may perform LBT in the same subframe. Thefollowing figure is an example configuration and differentconfigurations may be implemented based on network design requirements.

In an example, the configuration of the subset of subframes employed forLBT may be coordinated among multiple base stations (eNBs). The eNBs maydirectly communicate with each other. For example, a first eNB maytransmit one or more first messages to a second eNB. The one or moremessages may comprise configuration parameters indicating the subset ofsubframes employed for LBT for one or more LAA cells. In an exampleembodiment, the first and second eNB may receive their LBT subframeconfiguration from another network node. In an example embodiment, anetwork node may coordinate LBT subframe configuration among a pluralityof base stations.

According to some of the various aspects of embodiments, LBT resourcepartitioning may be employed for interference management and/or loadbalancing in co-channel deployments. To reach its full potential,resource partitioning may be paired withinterference-cancellation-capable wireless devices. Similar approachesmay be applied to micro, pico, femto, and relay nodes. Each node mayhave its own mechanisms. For example, the X2 backhaul link between themacro and relay base stations may be over an LTE air interface. Inanother example, closed femto cells may create their own interferencechallenges. Femto base stations may or may not include an X2 interfaceand employ static or dynamic interference management methods usingOAM-based or similar solutions.

According to some of the various aspects of embodiments, adaptive LBTcontrol for LAA in LTE may be enabled through X2 backhaul coordinationof resources used for LBT subframes. According to some of the variousaspects of embodiments, adaptive LBT control for LAA in LTE may beenabled through a third network node coordinating resources used for LBTsubframes. In another example, LBT subframes may be preconfigured in aneNB. The granularity of the negotiated LBT resource may be a subframe.One of the various motivations behind resource partitioning may be tocontrol channel access among multiple network nodes. In an example, LBTsubframes may be coordinated among eNBs of different service providers.The coordination may be performed directly or indirectly via a networknode.

In an example embodiment, LBT resources may be coordinated amongdifferent service providers in a given area. A given service providermay be assigned its own subset of subframes for performing LBT. Thegiven service provider, may assign a first subset of the subset ofsubframes to an eNB in the given service provider. The eNBs in the givenservice operator network may coordinate the use of LBT subframes amongthemselves. In an example embodiment, the LBT subframes assigned to agiven service provider may dynamically change. A third network node maycoordinate the assignment of LBT subframes among different serviceprovides. Then a given service provider may assign the obtained LBTsubframes among eNBs of the given service provider in a coverage area.

In an example embodiment, a central database may store the LBT subframeconfiguration of different service operators and/or eNBs. A serviceprovider node (e.g. eNB or another network node) may communicate withthe central database and receive a message comprising configurationinformation about LBT subframes for the service provider and/or otherservice providers in a specific area. A service provider node mayrequest for information on LBT configuration. The request may comprise asuggested LBT subframe, and/or may include a request for informationabout the available LBT subframes. The service operator may receive anassignment of LBT subframes from the central database. The LBT subframeconfiguration of one or more base station in the specific coverage areamay be based on the configuration parameters received from the centraldatabase.

In an example, a first node (e.g. an eNB) may transmit a message to oneor more second nodes (e.g. eNB) comprising configuration parameters(e.g. a bit map) indicating which resources may be utilized for LBT ofone or more unlicensed cell of the first node. The second nodes may bemade aware of the LBT subframe pattern from the first base station. Thesecond base station(s) may perform LBT in the cell in other subframesnot overlapping with the first base station LBT subframes. The messagemay comprise an eNB ID. The message may comprise an ID for an LAA cell,and LBT subframes configuration for the LAA cell.

In an example, a high-power node (macro base station) may inform thelow-power node (pico base station) of which resources may be utilizedfor LBT of one or more unlicensed cell. Low-power nodes may be madeaware of the LBT subframe pattern from a high-power base station and mayperform LBT in the cell in other subframes.

In an example implementation, an eNB may receive its LBT subframesconfiguration from another network node. In an example, an eNB mayderive its LBT subframes configuration parameters from configurationparameters received from another node. For example, eNB may derive itsLBT subframes configuration parameters from one or more parametersreceived from a network server. For example, eNB may derive its LBTsubframes configuration parameters from one or more parameters receivedfrom another eNB.

According to some of the various aspects of embodiments, the X2interface may enable direct base station to base station interfacecoordination for performing LBT. Co-channel deployments of unlicensedspectrum may require coordination of LBT subframes. LBT subframes maycoordinate LBT process and different nodes may not compete in starting aburst in a given subframe. On non-LBT subframes, base station may notstart a burst while it may transmit an already started burst.

LBT coordination using LBT subframes may be performed by means of abitmap. Each bit in the bitmap may be mapped to a single subframe. Thesize of the bitmap may be, for example, 40 bits, resulting in the LBTpattern repeating itself after 40 ms. In another embodiment, data may bescheduled in non-LBT subframes at a substantially lower power.

Communication of LBT subframe configuration between nodes may be peer topeer. Or it may be in a master-slave relationship. In an examplescenario, a macro base station may be a master, and a pico base stationmay be a slave. In an example scenario, a first type of base station maybe a master, and a second type of base station may be a slave. Inanother example, base stations may be selected as master and slaveaccording to a configuration parameter. In another example, a thirdnetwork node may coordinate and/or communicate LBT subframes amongmultiple base stations.

According to some of the various aspects of embodiments, subframeresource partitioning may create an interference pattern and/or loadbalancing that may require a new radio resource measurement paradigm.

In an example embodiment, a base station may broadcast an LBT subframeconfiguration. For example, the base station may employ MBSFN(multi-cast, broadcast, single frequency network) subframe configurationbroadcast or unicast messages. An example broadcast message is an RRCsystem information block. MBSFN or LBT subframe configurations mayinclude a radio frame allocation period, a radio frame allocationoffset, a subframe allocation bitmap, any combination of theseparameters, or the like. A radio frame allocation period may be 1, 2, 4,8, 16 or 32 frames. A radio frame allocation offset may be a numberbetween 1 to 7 subframes. A subframe allocation bitmap may be for oneframe or four frames. Radio frames that contain MBSFN/LBT subframes mayoccur when equation (SFN mod radio Frame Allocation Period=radio FrameAllocation Offset) is satisfied. Values 1 and 2 may not be applicable toradio frame allocation period when four Frames are used.

According to some of the various aspects of embodiments, a subframeallocation bitmap may define the subframes that are allocated for MBSFNwithin the radio frame allocation period defined by the radio frameallocation period and the radio frame allocation offset. A subframeallocation bitmap for one frame may be six bits long and for four framesmay be 24 bits long. In a bit-map indicating MBSFN/LBT subframeallocation in four consecutive radio frames, a “1” may denote that thecorresponding subframe is allocated for MBSFN/LBT. The bitmap may beinterpreted as follows: For FDD: Starting from the first radio frame andfrom the first/leftmost bit in the bitmap, the allocation may apply tosubframes #1, #2, #3, #6, #7, and #8 in the sequence of the fourradio-frames. For TDD: Starting from the first radio frame and from thefirst/leftmost bit in the bitmap, the allocation applies to subframes#3, #4, #7, #8, and #9 in the sequence of the four radio-frames. Thelast four bits may not be used. Uplink subframes may not be allocated.

Other example configurations may be implemented. For example, an MBSFNsubframe configuration may be used to introduce LBT subframes andsubframes used for scheduling release 13 or above wireless devices. Forexample, an MBSFN configuration may introduce subframe 1, 3, 6 and 8 asMBSFN subframes in a frame. Then MBSFN subframe 1 may be used forscheduling release 13 or above wireless devices, and MBSFN subframe 3,6, and 8 may be used as LBT subframes. Therefore, as seen in thisexample, MBSFN configuration may indicate other types of subframes inaddition to LBT. In another configuration, a base station may use one ormany of MBSFN subframes for broadcasting or multicasting services. In atypical scenario, in which MBSFN may be configured, for example, forfour frames, with a period of 40 msec, various configurations forcombining LBT, MBSFN, and release 10 or above subframes may be possible.In this specification, LBT subframes may be called LBT subframes.

A network may comprise a plurality of base stations. Transmission timemay be divided into a plurality of frames. Each frame in the pluralityof frames may further be divided into a plurality of subframes. A firstbase station may comprise a communication interface, a processor, and amemory storing instructions that, when executed, cause the first basestation to perform certain functions. According to some of the variousaspects of embodiments, the first base station may transmit a firstmessage to one or more wireless devices. The first message may comprisean initial subframe allocation bitmap indicating an initial plurality ofLBT subframes.

After an increase in the number of the plurality of wireless devices orafter an increase in the traffic load of the first base station by anamount greater than a load value, the first base station may transmit asecond message. The second message may comprise an updated subframeallocation bitmap indicating an updated plurality of LBT subframes. Theupdated plurality of LBT subframes may comprise a larger number of LBTsubframes than the initial plurality of LBT subframes.

The number of LBT subframes for a base station may increase or decreasedepending a network load. For example, when an eNB has higher load (e.g.compared with its neighboring node, or compared with its previous loador expected load), the number of LBT subframe for the eNB may increase.For example, when an eNB has a lower load (e.g. compared with itsneighboring node, or compared with its previous load or expected load),the number of LBT subframes for the eNB may decrease. An eNB maytransmit a message to another node (e.g. another eNB or a network node).The message may comprise the updated LBT subframe configuration. In anexample, the eNB may receive an updated LBT subframe configuration whenthe load increases or decreases from a network node. For example, theeNB may request for an updated LBT subframe configuration and mayreceive a response message comprising configuration parametersindicating the updated LBT subframes.

The configuration of LBT subframes may be controlled by a network node.In an example, the configuration of LBT subframes may be coordinated bydirect or indirect communication among eNBs employing X2 interface orany other interface.

Example embodiments enable dynamic configuration of LBT subframes anddynamic adaptation of LBT subframes in one or more base stations toadapt to changes in the traffic load of one or more base stations. Sucha dynamic configuration may increase air interface and backhauloverhead. Additional overhead in signaling may include additional RRCmessages and additional X2 application protocol messages. The gains inair interface efficiency maybe due to increase in the LBT subframes insome of the cells with relatively high load. This may reduce the packetcongestion in those cells and reduce packet transmission delay and/orpacket loss and may increase cell throughput. Some of the networksimulations/analysis shows that the benefits in air interface efficiencygains may be more than the negative impact due to additional overhead.

The example embodiments may add additional complexity in networkoperations, but instead it may increase the overall spectral efficiencyin the network. Improving battery power consumption in UE and/or eNB isanother benefit of the disclosed embodiments. The dynamic operation maybe triggered when the load is decreased by an amount greater than a loadvalue or decreased by an amount greater than a load value. The operationmay be performed selectively, by one or more base stations, and may becommunicated to one or more other base stations. This dynamicconfiguration is different from other methods employed to increase cellcapacity. It may require transmission and reception of additional RRCreconfiguration messages to reconfigure the air interface parameters inwireless devices in the coverage area and may require transmission andreception of additional X2 interface messages to other base stations.

There may be an X2 interface between the first base station and one ormore second plurality of base stations. After an increase in the numberof the first plurality of wireless devices, the first base station maytransmit a message to at least one second base station. The message maycomprise a first pattern bitmap indicating the updated first LBTsubframe allocation compared with the initial LBT subframe allocation.

In an example embodiment, frame transmissions are substantiallysynchronized among different base stations. System frame numbertransmissions are synchronized among different base stations. Forexample, the same system frame number may be transmitted during framestransmitted substantially synchronously. Different cells of the samebase station and different cells belonging to different base stationsmay transmit the same system frame number during the same frame that istransmitted substantially at the same time. Example embodiments, amongother things, may enable an efficient configuration of LBT subframes inone or more base stations and/or may enable a more efficient loadbalancing and interference management. Such a synchronization amongcells of the same base station and cells belonging to different basestations may increase backhaul overhead and network complexity.Additional complexity in network architecture may include additionalmechanisms for frame synchronization among different base stations aswell as mechanisms for synchronization in transmitting the same systemframe number during synchronized frames.

In an example embodiment, GPS assisted or packet based synchronizationmechanisms may be enhanced to include SFN synchronization among the basestations. The gains in air interface efficiency maybe due to loadbalancing and reduction in inter-cell interference. This may reduce thepacket loss and may increase cell throughput. Some of the networksimulations/analysis shows that the benefits in air interface efficiencygains may be more than the negative impact due to additional networkcomplexity and overhead. The example embodiments may add additionalcomplexity in network operations, but instead it may increase theoverall spectral efficiency in the air interface. The synchronizedoperation may be triggered if the advantages in SFN synchronization ismore beneficial compared to disadvantages due to the additional networkcomplexity. Therefore, the operation may be performed selectively, byone or more base stations. This synchronized configuration is differentfrom other network synchronization methods employed in, for example, TDDsystems. It may require transmission and reception of additionalmessages to ensure synchronization in system frame number transmission(the same number is transmitted during the simultaneous frames ofdifferent base stations). This mechanism may require transmission andreception of additional X2 and/or S1 interface messages or additionalGPS assisted mechanisms.

In an example embodiment, a system frame number coordinator maycoordinate the transmission of the same system frame number in frames ofdifferent base stations. Control messages may trigger multiple basestations to start or re-start the SFN transmission at the same timestarting from the same initial number. This mechanism requiresadditional complexity compared with transmission of the same SFN inframes of different cells of the same base station, since it requiresprotocols/mechanisms for coordination among many base stations. When anew base station is added to the network, additional mechanisms may berequired to communicate with the new base station and ensure that thenew base station transmits the same system frame number along with otherbase stations in the network. This may be achieved via control messagestransmitted via X2 and/or S1 interface. In an example embodiment, asystem frame number coordinator may communicate/transmit messages to theexisting and new base stations to synchronize SFN transmission.Distributed algorithms and/or GPS bases algorithms may also be developedto ensure SFN synchronization among base stations.

In an example embodiment, LBT configuration may be included for examplein the load indication message transmitted via X2 interface. In anexample a first base station may transmit a message (e.g. loadindication) indicating LBT parameters. For example, LBT parameters mayinclude statistics on LBT success and/or failure rates. For example, aneNB may transmit a message to a second eNB indicating the duration inwhich the LBT was not successful. In an example embodiment, LBTconfiguration and/or one or more parameters in the load indicationmessage may be transmitted to and/or received from a network node.

In an example, an eNB may initiate a load indication procedure bysending load information message to one or more eNBs controllingintra-frequency neighbouring cells.

In an example, if the UL Interference Overload Indication IE is receivedin the load information message, it may indicate the interference levelexperienced by the indicated cell on all resource blocks, per PRB. Thereceiving eNB may take such information into account when setting itsscheduling policy and may consider the received UL Interference OverloadIndication IE value valid until reception of a new load informationmessage carrying an update of the same IE. If the UL High InterferenceIndication IE is received in the load information message, it mayindicate, per PRB, the occurrence of high interference sensitivity, asseen from the sending eNB. The receiving eNB may try to avoid schedulingcell edge UEs in its cells for the concerned PRBs. The Target Cell ID IEreceived within the UL High Interference Information IE group in theload information message indicates the cell for which the correspondingUL High Interference Indication is meant. The receiving eNB may considerthe value of the UL High Interference Information IE group valid untilreception of a new load information message carrying an update.

In an example, if the Relative Narrowband Tx Power (RNTP) IE is receivedin the load information message, it indicates, per PRB, whether downlinktransmission power is lower than the value indicated by the RNTPThreshold IE. The receiving eNB may take such information into accountwhen setting its scheduling policy and shall consider the receivedRelative Narrowband Tx Power (RNTP) IE value valid until reception of anew load information message carrying an update. If the ABS InformationIE is included in the load information message, the ABS Pattern Info IEmay indicate the subframes designated as almost blank subframes by thesending eNB for the purpose of interference coordination. The receivingeNB may take such information into consideration when scheduling UEs.

In an example, the receiving eNB may use the Measurement Subset IEreceived in the load information message, for the configuration ofspecific measurements towards the UE. The receiving eNB may consider thereceived information as immediately applicable. The receiving eNB mayconsider the value of the ABS Information IE valid until reception of anew load information message carrying an update. If an ABS indicated inthe ABS pattern info IE coincides with a MBSFN subframe, the receivingeNB may consider that the subframe is designated as almost blanksubframe by the sending eNB. If the Invoke Indication IE is included inthe load information message, it indicates which type of information thesending eNB would like the receiving eNB to send back. The receiving eNBmay take such request into account. If the Invoke Indication IE is setto “ABS Information”, it indicates the sending eNB would like thereceiving eNB to initiate the Load Indication procedure, with the loadinformation message containing the ABS Information IE indicatingnon-zero ABS patterns in the relevant cells.

In an example, LBT subframe configuration may be included for example inthe load indication message transmitted via X2 interface. LBT subframeconfiguration may indicate one or more subframes as LBT subframes. In anexample a first base station may transmit a message (e.g. loadindication) indicating LBT parameters. For example, LBT parameters mayinclude LBT thresholds and/or offsets and/or timer/counter information,and/or statistics on LBT success and/or failure information. Forexample, a first eNB may transmit a message to a second eNB indicatingthe duration in which the LBT was not successful, or LBT success/failurerates in one or more subframes. The first eNB may employ the informationin handover, or updating cell configurations. In an example embodiment,LBT configuration and/or one or more parameters in the load indicationmessage may be transmitted to and/or received from a network node.

FIG. 13 is an example flow diagram as per an aspect of an embodiment ofthe present invention. The flow diagram may be processed as a method.The flow diagram may be executed by a base station. The base station maycomprise one or more processors and memory storing instructions that,when executed, cause the base station to perform actions described inthe flow diagram.

The base station may transmit at least one message at 1310. The at leastone message may comprise comprising one or more first parameters. Theone or more first parameters may identify one or more subframes as alisten-before-talk (LBT) subframe. At 1320, an LBT procedure may beperformed in a subframe in the one or more subframe. A burst may betransmitted at 1340 when the LBT procedure indicates a clear channel(1330). The burst may be configurable to start in the subframe if thesubframe is identified as an LBT subframe.

According to an embodiment, the one or more first parameters comprise abitmap. According to an embodiment, the one or more first parameters mayindicate a periodic pattern for the one or more subframes. According toan embodiment, a message in the at least one message may comprise aradio resource control (RRC) message. According to an embodiment, the atleast one message may comprise a second parameter indicating a maximumduration for the burst. According to an embodiment, the at least onemessage may comprise one or more LBT parameters. According to anembodiment, the one or more subframes may be associated with a licensedassisted access (LAA) cell.

FIG. 14 is an example flow diagram as per an aspect of an embodiment ofthe present invention. The wireless device may be processed as a method.The flow diagram may be executed by a wireless device. The wirelessdevice may comprise one or more processors and memory storinginstructions that, when executed, cause the wireless device to performactions described in the flow diagram.

The wireless device may receive at least one message at 1410. The atleast one message may comprise one or more first parameters. The one ormore first parameters may identify one or more subframes as alisten-before-talk (LBT) subframe. At 1420, the base station may monitora channel of a starting subframe of a burst. The burst may beconfigurable to begin in the starting subframe if the starting subframeis identified as an LBT subframe.

According to an embodiment, the one or more first parameters maycomprise a bitmap. According to an embodiment, a message in the at leastone message may comprise a radio resource control (RRC) message.According to an embodiment, the one or more subframes may be associatedwith a licensed assisted access (LAA) cell. According to an embodiment,the one or more first parameters may indicate a periodic pattern for theone or more subframes. According to an embodiment, the at least onemessage may comprises a second parameter indicating a maximum durationfor the burst. According to an embodiment, the at least one message maycomprise one or more LBT parameters.

FIG. 15 is an example flow diagram as per an aspect of an embodiment ofthe present invention. The flow diagram may be processed as a method.The flow diagram may be executed by a base station. The base station maycomprise one or more processors and memory storing instructions that,when executed, cause the base station to perform actions described inthe flow diagram.

A first base station may receive a first message at 1510. The firstmessage may comprise one or more first parameters. The one or more firstparameters may identify one or more first subframes as alisten-before-talk (LBT) subframe. One or more second subframes may beselected at 1520 as an LBT subframe by the first base station employingthe one or more first parameters. An LBT procedure may be performed in asubframe in the one or more subframes at 1530. A burst may betransmitted at 1550 when the LBT procedure indicates a clear channel at1540.

According to an embodiment, the first base station may receive the firstmessage from a second base station. According to an embodiment, thefirst base station may receive the first message from a network server.According to an embodiment, the one or more second subframes are thesame as the one or more first subframes. According to an embodiment, theone or more second subframes exclude the one or more first subframes.According to an embodiment, the one or more second subframes are asubset of the one or more first subframes. According to an embodiment,the one or more first parameters comprise a bitmap. According to anembodiment, the first message may comprise a load indication message.According to an embodiment, the first message comprises one or moresecond parameters indicating a maximum burst duration.

According to an embodiment, the base station may further transmit asecond message to a wireless device. The second message may comprise oneor more second parameters indicating the one or more second subframes.

In this specification, “a” and “an” and similar phrases are to beinterpreted as “at least one” and “one or more.” In this specification,the term “may” is to be interpreted as “may, for example.” In otherwords, the term “may” is indicative that the phrase following the term“may” is an example of one of a multitude of suitable possibilities thatmay, or may not, be employed to one or more of the various embodiments.If A and B are sets and every element of A is also an element of B, A iscalled a subset of B. In this specification, only non-empty sets andsubsets are considered. For example, possible subsets of B={cell1,cell2} are: {cell1}, {cell2}, and {cell1, cell2}.

In this specification, parameters (Information elements: IEs) maycomprise one or more objects, and each of those objects may comprise oneor more other objects. For example, if parameter (IE) N comprisesparameter (IE) M, and parameter (IE) M comprises parameter (IE) K, andparameter (IE) K comprises parameter (information element) J, then, forexample, N comprises K, and N comprises J. In an example embodiment,when one or more messages comprise a plurality of parameters, it impliesthat a parameter in the plurality of parameters is in at least one ofthe one or more messages, but does not have to be in each of the one ormore messages.

Many of the elements described in the disclosed embodiments may beimplemented as modules. A module is defined here as an isolatableelement that performs a defined function and has a defined interface toother elements. The modules described in this disclosure may beimplemented in hardware, software in combination with hardware,firmware, wetware (i.e. hardware with a biological element) or acombination thereof, all of which are behaviorally equivalent. Forexample, modules may be implemented as a software routine written in acomputer language configured to be executed by a hardware machine (suchas C, C++, Fortran, Java, Basic, Matlab or the like) or amodeling/simulation program such as Simulink, Stateflow, GNU Octave, orLabVIEW MathScript. Additionally, it may be possible to implementmodules using physical hardware that incorporates discrete orprogrammable analog, digital and/or quantum hardware. Examples ofprogrammable hardware comprise: computers, microcontrollers,microprocessors, application-specific integrated circuits (ASICs); fieldprogrammable gate arrays (FPGAs); and complex programmable logic devices(CPLDs). Computers, microcontrollers and microprocessors are programmedusing languages such as assembly, C, C++ or the like. FPGAs, ASICs andCPLDs are often programmed using hardware description languages (HDL)such as VHSIC hardware description language (VHDL) or Verilog thatconfigure connections between internal hardware modules with lesserfunctionality on a programmable device. Finally, it needs to beemphasized that the above mentioned technologies are often used incombination to achieve the result of a functional module.

The disclosure of this patent document incorporates material which issubject to copyright protection. The copyright owner has no objection tothe facsimile reproduction by anyone of the patent document or thepatent disclosure, as it appears in the Patent and Trademark Officepatent file or records, for the limited purposes required by law, butotherwise reserves all copyright rights whatsoever.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example, and notlimitation. It will be apparent to persons skilled in the relevantart(s) that various changes in form and detail can be made thereinwithout departing from the spirit and scope. In fact, after reading theabove description, it will be apparent to one skilled in the relevantart(s) how to implement alternative embodiments. Thus, the presentembodiments should not be limited by any of the above describedexemplary embodiments. In particular, it should be noted that, forexample purposes, the above explanation has focused on the example(s)using FDD communication systems. However, one skilled in the art willrecognize that embodiments of the invention may also be implemented in asystem comprising one or more TDD cells (e.g. frame structure 2 and/orframe structure 3-licensed assisted access). The disclosed methods andsystems may be implemented in wireless or wireline systems. The featuresof various embodiments presented in this invention may be combined. Oneor many features (method or system) of one embodiment may be implementedin other embodiments. Only a limited number of example combinations areshown to indicate to one skilled in the art the possibility of featuresthat may be combined in various embodiments to create enhancedtransmission and reception systems and methods.

In addition, it should be understood that any figures which highlightthe functionality and advantages, are presented for example purposesonly. The disclosed architecture is sufficiently flexible andconfigurable, such that it may be utilized in ways other than thatshown. For example, the actions listed in any flowchart may bere-ordered or only optionally used in some embodiments.

Further, the purpose of the Abstract of the Disclosure is to enable theU.S. Patent and Trademark Office and the public generally, andespecially the scientists, engineers and practitioners in the art whoare not familiar with patent or legal terms or phraseology, to determinequickly from a cursory inspection the nature and essence of thetechnical disclosure of the application. The Abstract of the Disclosureis not intended to be limiting as to the scope in any way.

Finally, it is the applicant's intent that only claims that include theexpress language “means for” or “step for” be interpreted under 35U.S.C. 112, paragraph 6. Claims that do not expressly include the phrase“means for” or “step for” are not to be interpreted under 35 U.S.C. 112.

1. A method comprising: receiving, by a first base station from a secondbase station, one or more first parameters identifying a first pluralityof subframes as listen-before-talk (LBT) subframes of the second basestation; selecting a second plurality of subframes as LBT subframes bythe first base station based on the one or more first parameters;transmitting, by the first base station to a wireless device, at leastone radio resource control message comprising one or more thirdparameters identifying the second plurality of subframes as LBTsubframes; performing, by the first base station, an LBT procedure in asubframe of the second plurality of subframes; and transmitting, by thefirst base station, a burst based on the LBT procedure indicating aclear channel, wherein the burst is configurable to start in thesubframe based on the subframe being identified as an LBT subframe. 2.The method of claim 1, wherein the one or more first parameters comprisea bitmap.
 3. The method of claim 1, wherein the second plurality ofsubframes are associated with a licensed assisted access cell.
 4. Themethod of claim 1, wherein the one or more first parameters indicate aperiodic pattern for the second plurality of subframes.
 5. The method ofclaim 1, wherein the at least one radio resource control messagecomprises a second parameter indicating a maximum duration for theburst.
 6. The method of claim 1, wherein the at least one radio resourcecontrol message comprises one or more LBT parameters.
 7. A method ofclaim 1, further comprising transmitting, by the first base station tothe second base station, one or more second parameters identifying thesecond plurality of subframes as a listen-before-talk (LBT) subframe ofthe first base station.
 8. The method of claim 7, wherein the one ormore first parameters comprise a bitmap.
 9. The method of claim 8,wherein the second plurality of subframes are associated with a licensedassisted access cell.
 10. The method of claim 9, wherein the one or morefirst parameters indicate a periodic pattern for the second plurality ofsubframes.
 11. A base station comprising: one or more processors; andmemory storing instructions that, when executed, cause the base stationto: receive, from a second base station, one or more first parametersidentifying a first plurality of subframes as listen-before-talk (LBT)subframes of the second base station; select a second plurality ofsubframes as LBT subframes based on the one or more first parameters;transmit, to a wireless device, at least one radio resource controlmessage comprising one or more third parameters identifying the secondplurality of subframes as LBT subframes; perform an LBT procedure in asubframe of the second plurality of subframes; and transmit a burstbased on the LBT procedure indicating a clear channel, wherein the burstis configurable to start in the subframe based on the subframe beingidentified as an LBT subframe.
 12. The base station of claim 11, whereinthe one or more first parameters comprise a bitmap.
 13. The base stationof claim 11, wherein the second plurality of subframes are associatedwith a licensed assisted access cell.
 14. The base station of claim 11,wherein the one or more first parameters indicate a periodic pattern forthe second plurality of subframes.
 15. The base station of claim 11,wherein the at least one radio resource control message comprises asecond parameter indicating a maximum duration for the burst.
 16. Thebase station of claim 11, wherein the at least one radio resourcecontrol message comprises one or more LBT parameters.
 17. A base stationof claim 11, wherein the instructions that, when executed, further causethe base station to transmit to the second base station, one or moresecond parameters identifying the second plurality of subframes as alisten-before-talk (LBT) subframe of the base station.
 18. The basestation of claim 17, wherein the one or more first parameters comprise abitmap.
 19. The base station of claim 18, wherein the second pluralityof subframes are associated with a licensed assisted access cell. 20.The base station of claim 19, wherein the one or more first parametersindicate a periodic pattern for the second plurality of subframes.